Micro surgical instrument and loading unit for use therewith

ABSTRACT

A loading unit for engagement with a surgical instrument. The loading unit includes a proximal body portion, an end effector, an actuation sled, and pushers. The actuation sled is longitudinally translatable within a cartridge assembly. The pushers are disposed within the cartridge assembly. Each pusher includes a camming surface configured for engagement with the actuation sled. The camming surface of each pusher in a first row is longitudinally aligned with the camming surface of each pusher in a second row. The first row of pushers is laterally offset from the second row of pushers.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation Application which claims thatbenefit of and priority to U.S. patent application Ser. No. 14/873,500,filed on Oct. 2, 2015, the entire content of which is incorporatedherein by reference.

BACKGROUND Technical Field

The present disclosure relates generally to instruments for surgicallyjoining tissue and, more specifically, to a surgical fasteninginstrument and a loading unit including an end effector having arelatively small diameter.

Background of Related Art

Various types of surgical instruments used to surgically join tissue areknown in the art, and are commonly used, for example, for closure oftissue or organs in transection, resection, anastomoses, for occlusionof organs in thoracic and abdominal procedures, and forelectrosurgically fusing or sealing tissue.

One example of such a surgical instrument is a surgical staplinginstrument, which may include an anvil assembly, a cartridge assemblyfor supporting an array of surgical fasteners, an approximationmechanism for approximating the cartridge and anvil assemblies, and afiring mechanism for ejecting the surgical fasteners from the cartridgeassembly.

Using a surgical instrument, it is common for a surgeon to approximatethe anvil and cartridge members. Next, the surgeon can fire theinstrument to emplace surgical fasteners in tissue. Additionally, thesurgeon may use the same instrument or a separate instrument to cut thetissue adjacent or between the row(s) of surgical fasteners.

Additionally, a loading unit (e.g., a single use loading unit or adisposable loading unit) may be attached to an elongated or endoscopicportion of a surgical stapling instrument. Such loading units allowsurgical stapling instruments to have greater versatility, for example.The loading units may be configured for a single use, and/or may beconfigured for multiple uses.

Further, end effectors and/or loading units are generally limited insize by various components contained therein. That is, while there maybe a need for end effectors and/or loading units having diameters thatare smaller than those typically available, the diameter of the endeffector and/or loading unit is typically limited by the size, geometryand/or orientation of the staple pushers, I-beam, actuation sled, andfasteners, for example, contained therein.

SUMMARY

The present disclosure relates to a loading unit configured forengagement with a surgical instrument. The loading unit includes aproximal body portion, an end effector, an actuation sled, and pushers.The proximal body portion defines a longitudinal axis. The end effectoris disposed in mechanical cooperation with the proximal body portion,and includes a cartridge assembly and an anvil assembly. One of thecartridge assembly and the anvil assembly is movable with respect to theother of the cartridge assembly and the anvil assembly between an openposition and an approximated position to capture tissue therebetween.The cartridge assembly is configured to house fasteners therein. Theactuation sled is longitudinally translatable within the cartridgeassembly. The pushers are disposed within the cartridge assembly. Thepushers are arranged in first and second rows. Each pusher includes acamming surface configured for engagement with the actuation sled. Thecamming surface of each pusher in the first row is longitudinallyaligned with the camming surface of each pusher in the second row. Thefirst row is laterally offset from the second row.

In disclosed embodiments, the one camming surface of each pusherincludes a first camming surface and a second camming surface. It isfurther disclosed that the actuation sled is configured to contact thefirst camming surface of each pusher in the first row during distaltranslation of the actuation sled, and that the actuation sled isconfigured to contact the second camming surface of each pusher in thesecond row during distal translation of the actuation sled.Additionally, the second camming surface of each pusher in the first rowis spaced apart from the actuation sled during distal translation of theactuation sled, and the first camming surface of each pusher in thesecond row is spaced apart from the actuation sled during distaltranslation of the actuation sled.

It is also disclosed that the pushers are arranged in a third row and afourth row. Further, the actuation sled includes a first wedge and asecond wedge. Distal translation of the actuation sled causes the firstwedge to contact the camming surface of each pusher in the first row andthe second camming surface of each pusher in the second row. Distaltranslation of the actuation sled causes the second wedge to contact thefirst camming surface of each pusher in the third row and the secondcamming surface of each pusher in the fourth row.

It is further disclosed that an outer-most diameter of the end effectoris about 5 mm.

In disclosed embodiments, the loading unit includes a plurality ofT-shaped retention slots extending through a tissue-contacting surfaceof the cartridge assembly.

It is also disclosed that each pusher in the first row is disposed in afirst orientation, and each pusher in the second row is disposed in asecond orientation. The first orientation is offset 180° from the secondorientation.

Further, it is disclosed that each pusher in the first row is the sameas each pusher in the second row.

In disclosed embodiments, the first camming surface is disposed at afirst angle with respect to the longitudinal axis, the second cammingsurface is disposed at a second angle with respect to the longitudinalaxis, and the first angle is the same as the second angle. It isdisclosed that the first angle is between about 20° and about 40°.

It is further disclosed that each pusher includes a body portionincluding an upper edge configured to engage a fastener, a lateralextension extending perpendicularly from the body portion, a first legextending in a first direction from the lateral extension and having afirst camming surface, and a second leg extending in a second directionfrom the lateral extension and having a second camming surface. Theupper edge of the lateral extension is co-planar with the upper edge ofthe body portion.

The present disclosure also relates to a pusher for use with a surgicalinstrument. The pusher includes a body portion, a lateral extension, afirst leg and a second leg. The body portion includes an upper edgeconfigured to engage a fastener. The lateral extension extendsperpendicularly from the body portion. The first leg extends in a firstdirection from the lateral extension and includes a first cammingsurface. The second leg extends in a second direction from the lateralextension and includes a second camming surface.

In disclosed embodiments, an upper edge of the lateral extension isco-planar with the upper edge of the body portion.

It is further disclosed that the first camming surface is disposed at afirst angle with respect to the longitudinal axis, the second cammingsurface is disposed at a second angle with respect to the longitudinalaxis, and the first angle and the second angle are the same.Additionally, it is disclosed that the first angle is between about 20°and about 40°. It is also disclosed that the first direction is oppositefrom the second direction.

BRIEF DESCRIPTION OF FIGURES

Various embodiments of the presently disclosed surgical instruments andloading units are disclosed herein with reference to the drawings,wherein:

FIG. 1 is a perspective view of a surgical instrument in accordance withan embodiment of the present disclosure;

FIG. 2 is a perspective view of a loading unit having an end effector inaccordance with the present disclosure;

FIG. 3 is a perspective view of the loading unit of FIG. 2 illustratingthe end effector disposed in an articulated position;

FIG. 4 is a perspective view of the end effector of FIG. 3 in an openposition;

FIG. 5 is a side view of the end effector of FIG. 4 in an approximatedposition;

FIG. 6 is a top view of a cartridge assembly of the end effector of FIG.4;

FIG. 7 is an assembly view of the end effector of FIG. 4;

FIG. 8 illustrates the area of detail indicated in FIG. 7;

FIGS. 9 and 10 are perspective views of an anvil assembly of the endeffector of FIG. 4;

FIGS. 11 and 12 are perspective views of a sled, pushers, and fastenersof the loading unit according to the present disclosure;

FIG. 12A is a perspective view of a pusher of FIGS. 11 and 12;

FIG. 13 is an assembly view of a portion of the anvil assembly and aspring of the loading unit of the present disclosure;

FIG. 14 is a perspective view of the proximal portion of the anvilassembly engaged with the spring of FIG. 13;

FIG. 15 is a side cross-sectional view of portions of the end effectortaken along line 15-15 of FIG. 4;

FIG. 16 illustrates the area of detail indicated in FIG. 15;

FIG. 17 is a side cross-sectional view of portions of the end effectortaken along line 17-17 of FIG. 4;

FIG. 18 illustrates the area of detail indicated in FIG. 17;

FIG. 19 is a perspective view of the end effector of the presentdisclosure in an approximated position;

FIG. 20 is a perspective view of a portion of the end effector of FIG.19;

FIG. 21 is a side cross-sectional view of the end effector of thepresent disclosure taken along line 21-21 in FIG. 20;

FIG. 22 illustrates the area of detail indicated in FIG. 21;

FIG. 23 is side a cross-sectional view of portions of the end effectorof the present disclosure;

FIG. 24 illustrates the area of detail indicated in FIG. 23;

FIG. 25 is a perspective view of the end effector of the presentdisclosure in an approximated position; and

FIG. 26 is an end cross-sectional view of the end effector of thepresent disclosure taken along line 26-26 in FIG. 25.

DETAILED DESCRIPTION

Embodiments of the presently disclosed surgical instrument, loading unitfor use therewith, and cartridge assembly for use therewith, aredescribed in detail with reference to the drawings, wherein likereference numerals designate corresponding elements in each of theseveral views. As is common in the art, the term “proximal” refers tothat part or component closer to the user or operator, e.g., surgeon orphysician, while the term “distal” refers to that part or componentfarther away from the user.

A surgical instrument of the present disclosure is indicated asreference numeral 100 in FIG. 1. Generally, surgical instrument 100includes a handle assembly 110, an elongated portion 120 extendingdistally from handle assembly 110, and a loading unit 200 disposedadjacent a distal end of elongated portion 120. While FIG. 1 illustratessurgical instrument 100 including a powered handle assembly, other typesof handles can be used such as, for example, motor-driven, hydraulic,pivoting, ratcheting, etc. As used herein, “handle assembly” encompassesall types of handle assemblies. Loading unit 200 is releasablyattachable to elongated portion 120 of surgical stapling instrument 100,e.g., to allow surgical instrument 100 to have greater versatility. Thisarrangement allows the clinician to select a particular loading unit 200for a given procedure. As used herein, “loading unit” encompasses bothsingle use loading units (“SULU”) and disposable loading units (“DLU”).Additionally or alternatively, surgical instrument 100 may have acartridge that is removable and replaceable in the reusable jaws of theinstrument.

Examples of loading units for use with a surgical stapling instrumentare disclosed in commonly-owned U.S. Pat. No. 5,752,644 to Bolanos etal., the entire contents of which are hereby incorporated by referenceherein. Further details of an endoscopic surgical stapling instrumentare described in detail in commonly-owned U.S. Pat. No. 6,953,139 toMilliman et al., the entire contents of which are hereby incorporated byreference herein.

In surgical instrument 100 in accordance with the present disclosure, afiring rod (not explicitly shown) is moved distally through actuation ofhandle assembly 110 to deploy fasteners 600 (FIG. 7). With reference tothe embodiment illustrated in FIG. 1, at least a partial actuation offirst switch 112 or second switch 114 translates the firing rodlongitudinally. Distal translation of the firing rod causes distaltranslation of a knife bar 140 (FIG. 23), which causes distaltranslation of a clamping member 500 to approximate at least one jawmember with respect to the other, as discussed in further detail below.Further, distal translation of clamping member 500 (FIG. 2) causescorresponding translation of an actuation sled 520 (FIG. 16), whichresults in pushers 550 causing the ejection of fasteners 600 (FIG. 17)from pockets 401 (FIG. 6) of a cartridge assembly 400.

With additional reference to FIGS. 2 and 3, loading unit 200 of thepresent disclosure is shown. Loading unit 200 includes a proximal bodyportion 210 defining a longitudinal axis “A-A,” and a tool assembly orend effector 220 including a first jaw member or anvil assembly 300 anda second jaw member or cartridge assembly 400. Cartridge assembly 400includes a cartridge 408 disposed within a cartridge channel 409 (FIG.7). Proximal body portion 210 is configured to be removably attached toelongated portion 120 of surgical instrument 100 as will be discussed indetail hereinbelow. As shown in FIG. 3, end effector 220 is pivotablewith respect to the longitudinal axis “A-A.”

Referring now to FIG. 26, various features of loading unit 200 disclosedherein allow loading unit 200 to have a relatively small diameter “d”(such as, for example, about 4 mm, about 5 mm, about 6 mm, about 7 mm orabout 8 mm) as compared with more conventional instruments havingdiameters of about 12 mm. The diameter “d” of the loading unit 200, andend effector 220 in particular, is measured between a radiallyouter-most wall of anvil assembly 300 (or top portion 502 of clampingmember) and a radially outer-most wall of cartridge assembly 400 (orbottom portion 504 of clamping member 500). Such a low profile allowsloading unit 200 to be inserted into trocars “T” (shown in phantom inFIG. 5) or other access devices having similar inner diameters. It iscontemplated that the presently disclosed end effector 220 can beinserted into openings in body tissue (e.g., incision or naturallyoccurring orifice) having a comparable diameter. As can be appreciated,such low profile loading units 200 are useful in pediatric surgeriesand/or other thin tissue locations, for example. Additionally, in theillustrated embodiments, a proximal portion 212 of proximal body portion210 of loading unit 200 is sized and configured to engage elongatedportion 120 of surgical instrument 100 (FIG. 1) having a larger-diameterelongated portion 120 (e.g., between about 7 mm and about 12 mm), thusenabling greater versatility by allowing the loading unit 200 to becoupled to instruments having an elongated portion 120 with an outerdiameter between about 7 mm and about 12 mm.

More particularly, with reference to FIG. 2, an insertion tip 202 ofloading unit 200 is linearly inserted into the distal end of elongatedportion 120 of surgical stapling instrument 100 (FIG. 1). Nubs 204 ofinsertion tip 202 move linearly through slots formed adjacent the distalend of elongated portion 120. Subsequently, loading unit 200 is rotatedabout the longitudinal axis “A-A” such that nubs 204 move transverselywith respect to longitudinal axis “A-A” through the slots withinelongated portion 120. Additionally, during engagement of loading unit200 and elongated portion 120, the firing rod of handle portion 110engages knife bar 140 (FIG. 23) of loading unit 200.

With reference to FIGS. 7 and 26, clamping member 500 includes anI-shaped cross-section, including a top portion 502, which is configuredto engage anvil assembly 300, a bottom portion 504, which is configuredto engage cartridge assembly 400, and a vertical portion 503, whichconnects top portion 502 and bottom portion 504 and which may include acutting edge 506 on its distal or leading surface. Further, distaladvancement of clamping member 500 through end effector 220 causes topportion 502 to contact a camming surface 302 of anvil assembly 300 (FIG.16). Continued distal advancement of clamping member 500 thus causesanvil assembly 300 to pivot with respect to cartridge assembly 400 fromits open position (FIG. 4) toward its approximated position (FIG. 5).Further, top portion 502 of clamping member 500 is advanced distallywithin a slot 304 within anvil assembly 300, and bottom portion 504 ofclamping member 500 is distally advanced within a slot 414 withincartridge channel 409 of cartridge assembly 400 to help stabilize thejaw members with respect to each other and to help maintain a constantgap between the first and second jaw members 300, 400. Thus, apredetermined amount of distal travel of the firing rod causesapproximation and stabilization of jaw members. Additionally, cuttingedge 506 of clamping member 500, if included on clamping member 500,travels through a channel 305 (FIG. 9) of anvil assembly 300, a channel405 (FIG. 8) of cartridge assembly 400, and severs tissue disposedbetween the jaw members (and after the tissue has been fastened, asdiscussed above).

Additionally, with particular reference to FIGS. 13 and 14, a biasingelement 540 is configured to bias anvil assembly 300 toward the openposition. In particular, biasing element 540 (e.g., a spring) isdisposed at or secured to a proximal end of anvil assembly 300. As shownin FIGS. 16 and 22, for example, biasing element 540 contacts a distalend 213 of proximal body portion 210. An end 542 (e.g., a cantileveredend) of biasing element 540 is urged proximally, thus biasing anvilassembly 300 toward its open position (FIG. 15).

With further regard to actuation sled 520, distal translation ofactuation sled 520 sequentially engages a plurality of pushers 550, andcauses pushers 550 to move toward tissue-contacting surface 410 (FIG. 8)of cartridge assembly 400 and eject fasteners 600 towards anvil assembly300. Subsequent to the ejection of fasteners 600, cutting edge 506 ofclamping member 500 severs the stapled tissue (FIG. 18).

With particular reference to FIGS. 11 and 12, further details ofactuation sled 520 are disclosed. Actuation sled 520 includes two angledwedges 524 a, 524 b configured to contact either a first camming surface560 or a second camming surface 561 of pusher 550, thus causing upperedges 553 of pushers 550 to engage fasteners 600, and subsequently causeejection of fasteners 600 through retention cavities 450 of cartridgeassembly 400 (FIG. 8), and toward respective pockets 320 (FIG. 10) ofanvil assembly 300 (e.g., through tissue held between the jaw members).

Referring now to FIG. 12A, further details of pusher 550 are disclosed.Each pusher 550 includes a body portion 552, a lateral extension 554, afirst leg 556, a second leg 558, a first camming surface 560, and asecond camming surface 561. Each pusher 550 is positioned withincartridge assembly 400 such that body portion 552 is parallel to thelongitudinal axis “A-A” (see FIGS. 2, 7 and 8). Upper edge 553 of bodyportion 552 is configured and dimensioned to engage a backspan 602 offastener 600. Lateral extension 554 extends perpendicularly from bodyportion 552. In the illustrated embodiment an upper edge 555 of lateralextension 554 is co-planar with upper edge 553 of body portion 552.

In the orientation illustrated in FIG. 12A, first leg 556 extendsproximally from lateral extension 554, and second leg 558 extendsdistally from lateral extension 554. In this first orientation, pusher550 is used in connection with inside rows “I1” and “I2” of fasteners600 (FIG. 8). As can be appreciated, when the orientation of pusher 550is rotated 180°, pusher 550 is in its second orientation and is used inconnection with outside rows “O1” and “O2” of fasteners 600 (FIG. 8).Additionally, in the second orientation, first leg 556 extends distallyfrom lateral extension 554, and second leg 558 extends proximally fromlateral extension 554.

With continued reference to FIG. 12A, each of the first leg 556 andsecond leg 558 is generally wedge-shaped, and includes respectivecamming surfaces 560, 561 at its lower end and a planar surface 562 atits upper end. First camming surface 560 is disposed at a first angle α1with respect to an axis defined by a lower surface 556 a of first leg556, and second camming surface 561 is disposed at a second angle α2with respect to the axis defined by the lower surface 556 a of first leg556. The first angle α1 is the same as the second angle α2, and may bebetween about 20° and about 40°, for example. Larger and smaller anglesare also contemplated.

When pusher 550 is in the first orientation (FIG. 12A), camming surface560 of first leg 556 is configured to engage wedge 524 (wedge 524 a or524 b, depending on the row, as discussed below) of actuation sled 520,while camming surface 561 of second leg 558 is configured to be freefrom engagement with camming surface 524 of actuation sled 520. That is,in the first orientation, camming surface 561 does not contact or engagewedge 524. When pusher 550 is in the second orientation, camming surface561 of second leg 558 is configured to engage wedge 524 (wedge 524 a or524 b, depending on the row) of actuation sled 520, while cammingsurface 560 of first leg 556 is configured to be free from engagementwith wedge 524 of actuation sled 520. That is, in the secondorientation, camming surface 560 does not contact or engage wedge 524.

Additionally, as shown in FIG. 8, pushers 550 are arranged in fourlongitudinal rows “R1,” “R2,” “R3,” and “R4” where rows “R1” and “R2”are staggered on a first lateral side of channel 405, and rows “R3” and“R4” are staggered on a second lateral side of channel 405. Here,camming surface 560 of first leg 556 of pushers 550 arranged in row “R1”are longitudinally aligned with camming surface 561 of second leg 558 ofpushers 550 arranged in row “R2.” Similarly, camming surface 560 offirst leg 556 of pushers 550 arranged in row “R3” are longitudinallyaligned with camming surface 561 of second leg 558 of pushers arrangedin row “R4.” Accordingly, each wedge 524 a, 524 b of actuation sled 520is configured to engage two rows of pushers 550. More particularly,first wedge 524 a is configured to engage pushers 550 in rows “R1” and“R2,” while second wedge 524 b is configured to engage pushers 550 inrows “R3” and “R4.”

The pushers are the same in the rows R1, R2, R3, and R4, but arearranged in opposite orientations from adjacent rows. The first leg andsecond leg have camming surfaces that face in opposite directions toallow the pushers to be used in R1 and R2, for example, but in oppositeorientation. The lateral extensions in adjacent rows extend in oppositedirections. With the pushers in adjacent rows, such as pushers in R1 andR2 for example, the lateral extensions are accommodated with a smallarea because the pushers (and staples) are staggered with respect to oneanother.

With particular reference to FIG. 12A, planar surfaces 562 of first leg556 and second leg 558 of pusher 550 are parallel to upper edge 553 ofbody portion 552, but are not co-planar with upper edge 553. It isenvisioned that planar surfaces 562 contact or substantially contact anundersurface 407 within cartridge assembly 400 after pushers 550 aremoved or cammed by actuation sled 520 (see FIG. 24). That is,undersurface 407 within cartridge assembly 400 limits the travel ofpusher 550 toward anvil assembly 300, which may be helpful for ensuringthe complete and proper formation of fasteners 600, and may also behelpful to ensure pushers 550 remain within cartridge assembly 400(e.g., before, during, and after ejection of fasteners 600).

Referring back to FIG. 8, retention cavities 450 of cartridge assembly400 are shown. Each retention cavity 450 is T-shaped as it intersectstissue-contacting surface 410 to accommodate the travel of pusher 550 atleast partially therethrough. Additionally, similar to pushers 550,adjacent rows of retention cavities 450 are longitudinally staggeredfrom each other, and the orientation of retention cavities 450 isrotated 180° from retention cavities 450 in one adjacent row (see FIG.8, for example). It is envisioned that the T-shape of retention cavities450 helps maintain the lateral and longitudinal position of pushers 550within cartridge assembly 400.

While the above description contains many specifics, these specificsshould not be construed as limitations on the scope of the presentdisclosure, but merely as illustrations of various embodiments thereof.Therefore, the above description should not be construed as limiting,but merely as exemplifications of various embodiments. Those skilled inthe art will envision other modifications within the scope and spirit ofthe claims appended hereto.

What is claimed is:
 1. A loading unit configured for engagement with asurgical instrument, the loading unit comprising: an actuation sled; andpushers arranged in first and second rows, each pusher including a firstcamming surface configured for engagement with the actuation sled, thefirst camming surface of at least one pusher in the first row and thefirst camming surface of at least one pusher in the second row lie alonga common longitudinal axis, the first row of pushers laterally offsetfrom the second row of pushers, the at least one pusher in the first rowincluding a body portion having an upper edge configured to engage afastener, a lateral extension extending from the body portion, a firstleg extending in a first direction from the lateral extension andincluding the first camming surface, and a second leg extending in asecond direction from the lateral extension and including a secondcamming surface, wherein the upper edge of the lateral extension isco-planar with the upper edge of the body portion.
 2. The loading unitaccording to claim 1, wherein the at least one pusher in the second rowfurther includes a second camming surface.
 3. The loading unit accordingto claim 2, wherein the actuation sled is configured to contact thefirst camming surface of the at least one pusher in the first row duringdistal translation of the actuation sled, and the actuation sled isconfigured to contact the second camming surface of the at least onepusher in the second row during distal translation of the actuationsled.
 4. The loading unit according to claim 1, wherein the secondcamming surface of the at least one pusher in the first row is spacedapart from the actuation sled during distal translation of the actuationsled, and the first camming surface of the at least one pusher in thesecond row is spaced apart from the actuation sled during distaltranslation of the actuation sled.
 5. The loading unit according toclaim 1, wherein each pusher includes a lateral extension.
 6. Theloading unit according to claim 1, wherein an outer-most diameter of theloading unit is 5 mm.
 7. The loading unit according to claim 1, whereinan outer-most diameter of the loading unit is selected from the groupconsisting of: 4 mm, 5 mm, and 8 mm.
 8. The loading unit according toclaim 1, wherein the at least one pusher in the first row is disposed ina first orientation and the at least one pusher in the second row isdisposed in a second orientation, the first orientation is offset 180°from the second orientation.
 9. The loading unit according to claim 1,wherein the at least one pusher in the first row is the same as the atleast one pusher in the second row.
 10. The loading unit according toclaim 1, wherein the first camming surface of the at least one pusher inthe first row is disposed at a first angle, the second camming surfaceof the at least one pusher in the first row is disposed at a secondangle, and the first angle is the same as the second angle.
 11. Theloading unit according to claim 10, wherein the first angle is betweenabout 20° and about 40°.
 12. The loading unit according to claim 1,wherein the first camming surface of each pusher in the first row andthe first camming surface of each pusher in the second row lie along thecommon longitudinal axis.
 13. A pusher for use with a surgicalinstrument, comprising: a body portion including an upper edgeconfigured to engage a fastener; a lateral extension extending from thebody portion; a first leg extending in a first direction from thelateral extension and including a first camming surface, wherein anupper edge of the lateral extension is co-planar with the upper edge ofthe body portion; and a second leg extending in a second direction fromthe lateral extension and including a second camming surface.
 14. Thepusher according to claim 13, wherein the first camming surface isdisposed at a first angle, the second camming surface is disposed at asecond angle, and the first angle and the second angle are the same. 15.The pusher according to claim 13, wherein the first direction isopposite from the second direction.
 16. A loading unit configured forengagement with a surgical instrument, the loading unit comprising: aproximal body portion defining a longitudinal axis; a cartridge assemblydisposed in mechanical cooperation with the proximal body portion andconfigured to house fasteners therein, the cartridge assembly includinga tissue-contacting surface defining a plurality of T-shaped retentionslots; an actuation sled longitudinally translatable at least partiallywithin the cartridge assembly; and pushers disposed at least partiallywithin the cartridge assembly, the pushers arranged in first and secondrows, each pusher including a camming surface configured for engagementwith the actuation sled, wherein the camming surface of at least onepusher in the first row is longitudinally aligned with the cammingsurface of at least one pusher in the second row, the first row ofpushers laterally offset from the second row of pushers.